1. Field of the Invention
This invention relates to a recyclable slide fastener made of a synthetic resin or to a slide fastener made of a synthetic resin recyclable and also simultaneously dyeable in the same hue by post-dyeing or piece dyeing.
2. Description of the Prior Art
In recent years, the recovery and reclamation of industrial waste and discarded articles, or the so-called recycle, has been in vogue with a view to safeguarding the earth's environment and promoting the effective utilization of resources. In the case of such molded articles of thermoplastic substances as, for example, PET (polyethylene terephthalate) bottles, the practice of recovering used articles, remelting the articles, molding the melt, and putting the produced articles to reuse is now on the verge of being reduced to an enterprise.
In the case of slide fasteners, however, since the component parts thereof are numerous and further since they are made of various materials, the idea of separating such slide fasteners from discarded clothes, bags, tents, etc., recovering them as sorted into such different parts as sliders, fastener tapes, coupling elements, upper and lower stop members, and pin-and-box separators, and putting the recovered parts to reuse is nearly impracticable and has never been reduced to practice to date.
Every year the factories engaging in the manufacture of slide fasteners made of synthetic resins are yielding large volumes of waste plastic materials such as defective products, severed edges, and loose threads from their production lines as industrial waste. The disposal of these industrial waste calls for a huge expense. In the circumstances, the effective reclamation of these industrial waste has been growing into an increasingly important task.
The slide fasteners made of synthetic resins, in addition to the problems mentioned above, incur such problems as concern the properties which are expected of any slide fastener.
In the case of a slide fastener, owing to the discrepancies existing between the various mechanical properties thereof and the characteristics expected of the individual component parts thereof such as the durability thereof to withstand a sliding motion of the slider, it is considered difficult to manufacture all the component parts with synthetic resins. Further, in the reclamation of slide fasteners made of synthetic resins from the discarded plastic materials, since the individual parts are made of varying materials, the raw materials which are managed to be recovered as sorted at all inevitably suffer degradation of purity and, as a result, do not allow manufacture of products satisfying various characteristics expected of any slide fastener. The slide fasteners, therefore, defy all attempts at recycling them on the same principle as governs the recycle of such sundries as the PET bottles.
Then, the slide fasteners are possessed of decorative factors besides their functional factors. They are required to be dyed in various colors to meet diversified consumers' needs. Particularly in recent years, the desirability of manufacturing slide fasteners numerous in color yet small in lot size has come to find enthusiastic recognition. In the case of the slide fasteners made of synthetic resins which have been reclaimed from discharged plastic materials, however, since the raw materials themselves are already colored with various pigments and dyes, it is generally difficult to manufacture products whose component parts are harmoniously and homogeneously colored. The slide fasteners of such synthetic resins as have been reclaimed from the discarded plastic materials, therefore, are preferred to be simultaneously dyed in one and the same colors by means of the piece dyeing.
Even when newly produced synthetic resin materials (virgin materials) are used, however, since the individual component parts such as, for example, those used in fastener tape fibers and those used for the formation of coupling elements, are different in kind of synthetic resin and in kind and quantity of pigment, the fastener tapes and the coupling elements during the course of piece dyeing manifest difference in ability to absorb dye. In the case of an injection molded fastener, since the yarns used for forming the fastener tapes have been drawn in the process of production and the material injected for forming the coupling elements has not been drawn and, therefore, they manifest a difference in degree of crystallization, the fastener tapes and the coupling elements during the course of piece dyeing betray a difference in ability to absorb dye. As a result, it is difficult to dye simultaneously the individual component parts harmoniously and homogeneously. Worse still, it has been held that this simultaneous dyeing is impracticable when the injection molded fasteners use reclaimed plastic materials.